1. Field of the Invention
The invention relates to printing ink and more particularly to an aqueous printing ink vehicle and ink using a sulfated fatty acid component as a pigment binder.
2. Brief Description of the Prior Art
Conventional, commercially available printing inks, particularly useful for newsprinting, are generally made up of petroleum oils in which a pigment (preferably carbon black) is suspended. When applied to a paper substrate the oil separates from the pigment and is absorbed into the paper substrate. The pigment is left deposited on the paper surface, but "undried". In this "undried" state, offsetting may occur, i.e.; the ink is readily removed by rubbing the undried deposit.
There are a number of other disadvantages associated with the use of oil based printing inks, including "strike through", the phenomena caused by penetration of the oil component through the paper substrate so as to stain the reverse side. Many of these prior art problems associated with the use of oil based printing inks have been solved by the use of water-based printing inks; see for example U.S. Pat. No. 4,310,356.
The present invention is of water-based printing ink that is useful as a newsprint ink and also for printing on any porous surface such as cellulosic bags, boxes and the like. The ink of the invention is unique in that it includes as an active ingredient, a water-dispersible, sulfated organic binder based on a renewable resource and a co-binder useful for viscosity control. The inks of the invention are advantageous in that they are relatively non-polluting, may be applied by the flexographic technique (avoiding the energy inefficient letterpress technique), avoid "strike-through" and are rubresistant because they "dry" or bind on the substrate surface. The quality of printing achievable is high.